Various systems and methods have been devised for characterizing the occupant of a motor vehicle seat for purposes of determining whether air bag deployment should be allowed or suppressed in the event of a crash. For example, deployment is generally allowed in the case of a normally seated adult occupant, and suppressed in the case of a child seat placed on the vehicle seat and cinched down with a seat belt or child seat anchor. The occupant can usually be accurately and reliably characterized by measuring the occupant's seated weight, either with a fluid-filled seat bladder or a set of seat frame tension sensors. However, the occupant status can be ambiguous in the case of a child seat because cinching increases the apparent weight of the occupant. For this reason, it has been proposed to utilize auxiliary sensors to measure parameters such as the seat belt tension, and to recognize and distinguish between forward-facing and rearward-facing infant seats. Since such auxiliary sensors significantly increase the cost and installation complexity of an occupant detection system, it would be more desirable to devise a method for accurately and reliably characterizing seat occupants, including child seats, without auxiliary sensors.